As we celebrate the 50th anniversary of the Apollo 11 moon landing, NASA has started Artemis, a program that aims “to return astronauts to the lunar surface by 2024, including the first woman and the next man.”

Although both astronauts have enormous challenges ahead, the first woman will face added hurdles simply because everything in space carries the legacy of Apollo. It was designed by men, for men.

Not deliberately for men, perhaps, but women were not allowed in the astronaut program until the late 1970s, and none flew until Sally Ride became the first American woman in space, in 1983. By this point, the space program was built around male bodies.

If we do not acknowledge the gender bias of the early space program, it becomes difficult to move past it. One of the most compelling things about NASA is its approach to failure. Failure is not penalized in its culture; it is valued for the things that it can teach to save lives or resources in the future. As Bobak Ferdowsi, a systems engineer at NASA’s Jet Propulsion Laboratory has said, “our best mistakes are the ones we can learn from.”

What are the lessons to be learned from NASA’s failure to fly women during the Apollo era?

The most recent lesson emerged in April, when NASA had scheduled a spacewalk that was, quite by accident, staffed by two female astronauts. The agency had to restaff the spacewalk because it had only one spacesuit that was the correct size for both women.

This is not an indictment of NASA in 2019. But it does demonstrate a causal chain that begins with the Apollo program and leads through to present-day staffing choices.

The suits, known as extravehicular mobility units, were designed more than 40 years ago, based on the designs of the Apollo missions, at a time when all astronauts were men. Only four of the original 18 suits are still rated for spaceflight, and all of those are on the space station.

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Flight engineer Christina Koch at work on U.S. spacesuits in the International Space Station in April. She had been scheduled, along with Anne McClain, to perform the first all-female space walk on March 29, but spacesuits designed for men meant Chris Hague had to replace Ms. McClain on the walk.CreditNASA, via Associated Press

NASA first planned to have extra-small, small, medium, large and extra-large suits. For budget reasons, the extra-small, small and extra-large suits were cut. However, many of the male astronauts could not fit into the large suits, so the bigger size was brought back.

The smaller sizes never were.

Cady Coleman, an astronaut who has flown on two space shuttles and traveled to the space station, stands 5 feet 4 inches tall and remains the smallest person to ever qualify for a spacewalk. While she was training in NASA’s Neutral Buoyancy Lab, she had to improvise padding to wear inside her spacesuit.

Without that, smaller people would have an air bubble inside their suits that would make them spin in the lab’s pool as if a beach ball were strapped to their stomachs. It would not be a problem in space, Ms. Coleman told me. “But the N.B.L. was where people decided if you had what it takes to do a spacewalk,” she said.

And complaints? Well, no one else previously had that problem, so it must just be the person who complained. As a result, this gender bias became a mistake that we did not learn from, because the female astronauts compensated.

Inside the spacesuits, astronauts wear the liquid cooling and ventilation garment. This looks like long underwear covered with meters of tubes. It pumps water around the astronauts to cool them. Men and women wear the same style of garment despite the fact that we have different sweat patterns. Men sweat more than comparably fit women, and the areas where they sweat the most occur in different parts of the body. In other words, when it comes to temperature-controlling garments, the needs are different for men and women.

We are already aware of this in relation to office temperatures. Temperatures are set for men, which leaves women carrying sweaters to work.

A 2015 study by Dutch researchers found that indoor climate regulations were based on “an empirical thermal comfort model” developed in the 1960s. “Standard values for one of its primary variables — metabolic rate — are based on an average male, and may overestimate female metabolic rate by up to 35 percent,” they concluded.

NASA took pride in advertising the space shuttle as being a shirt-sleeve environment. And yet, if you watch “The Dream Is Alive,” a 1985 documentary made by crews aboard the shuttles, take note of the thick wool slippers on Kathryn Sullivan’s feet.

Women are asked to compromise about seemingly small things in order to participate. Every time we do that, we carry those imprints forward into the future.

It is worth looking back to the 1950s, when it seemed that women might be included in the early space program.

In the 1950s, before we had put anyone into space at all, Dr. Randolph Lovelace wondered how women would fare as space travelers. He had designed the tests for the Mercury astronauts and proceeded to put 19 women through the first round of assessments. Thirteen passed. In fact, from testing the “First Lady Astronaut Trainees,” Dr. Lovelace discovered that women might be better suited to space than men.

They were smaller, which would reduce the weight of payloads. They had better cardiovascular health and lower oxygen consumption. And they tolerated higher G-forces and outperformed men on isolation and stress tests. (One of the women was a mother of eight, and I imagine her looking at the tests and wondering when things would get difficult.)

Aviator Jerry Cobb with a Mercury capsule in 1961. She was one of the Mercury 13, a group of women who trained to be astronauts but never flew.CreditNASA

Despite all this, the tests were stopped. The women, later known as the Mercury 13, went to Congress to try to fight the ruling, but by then, the United States was in a moon race. Putting a woman into space was seen as a distraction, in part because the Soviet Union had already sent the first woman into space, Valentina Tereshkova, and that was derided as being just a publicity stunt.

This decision meant that by 1962 it was confirmed policy, as one NASA official wrote in a letter to a young girl who was interested in becoming an astronaut, that “we have no present plans to employ women on spaceflights because of the degree of scientific and flight training, and the physical characteristics, which are required.”

The gender bias in this statement is, to a modern reader, unmistakable.

During project Mercury, astronauts did not need scientific training — they simply needed a bachelor’s degree or equivalent. John Glenn did not even have a degree.

And the flight training — what did this mean, exactly? For project Mercury, astronauts needed to be a graduate of test pilot school, with a minimum of 1,500 hours flying time, and a qualified jet pilot.

The requirement to be a test pilot was a logical choice, not so much because of the nerves of steel required to fly experimental aircraft, but because test pilots are trained to take notes while piloting and to deliver clear reports afterward. But this criterion eliminated female pilots, because the only qualified test pilot schools were military and they did not accept women.

Mind you, during World War II, the Women Airforce Service Pilots were responsible for training pilots and towing planes for live-ammunition practice, as well as for ferrying and testing aircraft. In many cases, these women logged more flight hours than their male counterparts. They did not, however, have a certificate from a test pilot school.

Kari Love, a former spacesuit designer, once told me that “while we can look back and understand why women were an afterthought in aerospace to this point, we are at serious risk for that to be reproduced as we move into the commercial spaceflight era.”

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Astronaut Sunita Williams exiting an airlock on the International Space Station in 2012. She is a member of NASA’s commercial crew program and scheduled to fly on the Boeing Starliner in 2020.CreditNASA

Without conscious thought, the design of the ship and the lunar platform for the Artemis missions is likely to reproduce design choices made in the Apollo era when astronauts were all men.

Ladder rungs are set at the optimum distance for the average man. The pistol-grip tool, or cordless drill, is sized for a man’s hand.

Then there are the questions that we cannot answer simply because we have too little data. Since 1961, when Yuri Gagarin became the first man in space, over 500 people have been in space and only 64 of them have been women. We know that astronauts receive more radiation in space. Studies on Earth show that radiation can affect women at a rate 10 times higher than men. How will that play out in space?

As we look back at the Apollo mission and forward to Artemis, it is important to examine the gender biases of the early space program for lessons learned. If we want to land the first woman on the moon, let’s make sure she has tools designed with her in mind. Eliminating the legacy of gender bias is just one small step.

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Mary Robinette Kowal, a Hugo Award winner, is the author of “The Glamourist Histories” series, “Ghost Talkers” and the “Lady Astronaut” duology. Her work has appeared in Uncanny, Cosmos and Asimov’s.

Correction:July 19, 2019

An earlier version of this essay misstated the genders of people involved in testing of the SpaceX's Crew Dragon capsule. The testing included both men and women, not only men. It also incorrectly stated that an astronaut had completed a spacewalk. Cady Coleman qualified for a spacewalk, she did not perform one.

A version of this article appears in print on , Section F, Page 24 of the New York edition with the headline: In Space, Unisex Won’t Fly. Order Reprints | Today’s Paper | Subscribe